Hi Dave,
When I make mbTiles with SAS & Sat2Chart, I usually make them in sets of 5: ArcGIS, Bing, CMap,
Navionics, & GE (which comes out last because they get named "Satellite" for reasons
lost in history). I also make them with Zoom levels 10-18, so OpenCPN can pan & zoom easily (generally better than KAPs). We're in the
Philippines now, so the islands are fairly close together. Zoom 10 is fairly far out, so it doesn't have much detail but it covers a fairly large area.
CF makes it difficult to post a screen-shot (or I haven't learned the trick). You need to blow this up because it ended up wide, but at the bottom you can see 15 piano keys (all ON!
). I've turned off the first 2 to show a CMap image, which shows the effect better. The area in the extreme right is very detailed, the area in the middle not so much, & the area at the far left is even bigger (& fuzzier when I zoom in).
This is not a very good representation of the problem, but if I zoom in on the area to the left, all 15 piano keys are still displayed, since the mbTiles cover that area (at low res), but only 1 set of 5 is actually useful. The others are all too low resolution. But which one? I have to open them all to find out. And panning around changes which quintet is in focus, so I have to go looking all over again.
Since OpenCPN is (presumably) opening those mbTiles, I'd think it would know what zoom levels are available for the area displayed. What I'm proposing is for OpenCPN to not bother displaying the piano-keys for those mbTiles that only have imagery at significantly lower resolution than the
current display (OpenCPN zoom level, if you will). In the image here, the leftmost quintet of piano keys WOULD be displayed, because the area at right has good detail. But if I zoom in to the left, only the quintet for that area should be displayed.
And, of course, I'm proposing for OpenCPN to NOT turn mbTile piano keys ON until told to do so, the way it treats KAPs. I can't think of a good reason to have mbTiles default to On, but presumably there is one or they wouldn't default to On. If so, then maybe a preference switch (mbTiles default to ON [on/off]) would be a useful option.
At the risk of fuzzing up my above proposal, I'd also VERY much like mbTiles piano-keys to work like any other piano-keys, where clicking on a different piano key takes you to that chart, instead of having to turn each one on/off. I appreciate that mbTiles *can* have transparent sections, & some folks might want multiple mbTiles turned on at the same time, so again, I'd propose a user settable switch. The mbTiles produced by SAS seem to always be opaque, with no transparency, so having to turn each one on & off is a pain in the patootie (& breaks the nice original paradigm).
Thanks! Let me know if you'd like to see more
images.